Check your local regs before trying this!
Here, gizzard shad are bait fish. Eat alge and the like and won't hit lures ect.
American and hickory shad are considered game fish so cast nettting is out of bounds.
Use such rigs as a "shad dart" or "sabiki rig".
Please check local laws before doing this though.
As in how many of the second 2 can you posess at a time.

While bankfishing below a dam, I've seen gizzard/threadfin shad so thick that you could use a treble hook to snag enough to bait with, but that's not always something you can count on. About 75 miles downstream, the shad are so scarce that it's not unusual for it to take half an hour to get a dozen or so with a castnet.

Tie on about four or five small popeye type hair jig's and fish them fast towards the surface by swift water. Work's good for shad and skipjack's.
But as said cast net is probably best best. Snagging work's but is against kdw rule's within so many yard's from a dam but that is usualy where most of them are running.